This present application relates to rotor blades in gas turbine engines. More specifically, but not by way of limitation, the present application relates to the design and manufacture of rotor blades having hybrid airfoils for use in turbine engines.
Generally, combustion or gas turbine engines (hereinafter “gas turbines”) include compressor and turbine sections in which rows of blades are axially stacked in stages. Each stage typically includes a row of circumferentially-spaced stator blades, which are fixed, and a row of rotor blades, which rotate about a central turbine axis or shaft. In operation, generally, the compressor rotor blades are rotated about the shaft, and, acting in concert with the stator blades, compress a flow of air. This supply of compressed air then is used within a combustor to combust a supply of fuel. The resulting flow of hot expanding combustion gases, which is often referred to as working fluid, is then expanded through the turbine section of the engine. Within the turbine, the working fluid is redirected by the stator blades onto the rotor blades so to power rotation. The rotor blades are connected to a central shaft such that the rotation of the rotor blades rotates the shaft. In this manner, the energy contained in the fuel is converted into the mechanical energy of the rotating shaft, which, for example, may be used to rotate the rotor blades of the compressor, so to produce the supply of compressed air needed for combustion, as well as, for example, rotate the coils of a generator so to generate electrical power. During operation, because of the temperatures of the hot-gas path, the velocity of the working fluid, and the rotational velocity of the engine, the rotor blades within the turbine become particularly stressed with extreme mechanical and thermal loads.
Many industrial applications, such as those involving power generation and aviation, still rely heavily on gas turbines, and because of this, the engineering of more efficient engines remains an important objective. Even incremental advances in machine performance, efficiency, or cost-effectiveness provide a significant edge in the increasingly competitive markets affected by this technology. While there are several known strategies for improving the efficiency of gas turbines—such as, for example, increasing the size of the engine, increasing the temperatures through the hot-gas path, or increasing the rotational velocities of the rotor blades—each of these generally places additional strain on the blades and other hot-gas path components, which are already nearing the limits of conventional designs. As a result, there remains a need for improved apparatus, methods, and/or systems capable of alleviating such operational stresses or, alternatively, enhancing the durability of the components to better withstand them. This need is particularly evident in regard to turbine rotor blades, where marketplace competitiveness is exceedingly high and the many design considerations are interrelated and complex. As such, novel rotor blade designs, such as those presented herein, that balance these considerations in ways that optimize or enhance one or more desired performance criteria—while still adequately promoting structural robustness, part-life longevity, cost-effective engine operation, and/or the efficient usage of coolant—represent technological advances of considerable value.